79 Chapter 3 ASSESSMENT OF RISK P.R. Hunter, P. Payment, N. Ashbolt and J. Bartram 3.1 Introduction This chapter is primarily about the role of analytical techniques in the assessment of risk and specifically the value of water quality indicator parameters in this process. Assessment of risk in relation to drinking water supplies is undertaken for a number of reasons (Percival et al., 2000): • To predict the burden of waterborne disease in the community, under outbreak and non-outbreak conditions. This is helpful in determining the impact of improvements in water supply on health and to act as a driver towards improvement. • To help set microbial standards for drinking water supplies that will give tolerable levels of illness within the populations drinking that water. • To identify the most cost-effective option to reduce microbial health risks to drinking water consumers. • To help determine the optimum treatment of water to balance microbial risks against chemical risks from disinfection by-products. • To provide a conceptual framework to help individuals and organisations understand the nature and risk to, and from, their water and how those risks can be minimised. The focus of this chapter is to review the value of indicator parameters of water quality and other analyses in the context of three different approaches to the assessment of risk, namely:
